Dai,
TSV-1X Spearhead is an adaptation of one of Incat's ferry designs (Built right here in Australia ) under evaluation by the US. Essentially she is a fast sealift vessel, capable of 40+ knots, with a very shallow draft - (about 12 feet).
Extract from a news release,
28th October, 2003
New high tech, high-speed ship could rapidly deploy U.S. forces
Christopher Holton, WorldTechTribune.com
SPECIAL TO WORLD TRIBUNE.COM
The TSV also has substantial advantages over airlift.
Whereas the US Air Mobility Command’s largest transport, the C-5 Galaxy, can carry 2 M1 Abram tanks, the 98 meter TSV can carry 10—two reinforced platoons. The 112-meter TSV can carry 16 M1s, greater than an entire tank company. The USAF C-17 can carry just one M1 and the C-130 cannot lift the M1. Just as importantly, the TSVs can transport all of the tank crews with their tanks, which need little or no special preparation for the lift, which means they can literally roll off and be ready to fight at the destination.
The C-5 and the C-17 can carry two M2/M3 Bradley fighting vehicles. The C-130 cannot lift the Bradley. The 98-meter TSV can carry 20 Bradleys and the 112-meter TSV can carry 32 Bradleys—plus all of their crews!
(complete article here: http://www.incat.com.au/news/interest.cgi?caller=archive&news_task=DETAIL&articleID=63422§ionID=202)
General information here: http://www.incat.com.au/defence.cgi?task=TSV#
a PDF spec sheet here: http://www.incat.com.au/uploaded/18/63370_91spearheadspec.pdf
and the nearest thing to plans may be found here
There are some interesting "general arrangement" proposal diagrams for similar (98m) vessels too.
http://www.incat.com.au/display2.cgi?file=63208_1598muscgga.jpg&title=General%20Arrangement&type=ap
http://www.incat.com.au/display2.cgi?file=63207_2198mtsvga.jpg&title=General%20Arrangement&type=ap
http://www.incat.com.au/display2.cgi?file=63206_1998mmmga.jpg&title=General%20Arrangement&type=ap
Cheers,
Phil
Edit: Note that while I opened this post by saying she was "under evaluation", it should be noted that she has been used operationally in OIF.